Send one of your posts - HookMyApp

curl -X POST "https://gateway.hookmyapp.com/meta/v25.0/${INSTAGRAM_ACCOUNT_ID}/messages" \
  -H "Authorization: Bearer ${INSTAGRAM_ACCESS_TOKEN}" \
  -H "Content-Type: application/json" \
  -d '{
  "recipient": {
    "id": "17841400000000001"
  },
  "message": {
    "attachment": {
      "type": "MEDIA_SHARE",
      "payload": {
        "id": "17850000000000000"
      }
    }
  }
}'

payload.id is the media id of a post your account published.
Find your media ids in Your posts and profile.